It was bad. They also tested the CPU which was fin.
I put the new cpu along with the new motherboard into my computer and got a new error message "keyboard missing". I felt a sense of hope. It was crushed shortly after I plugged a keyboard in, and returned to my previous torment with "cpu failure"
I'm tempted to take the whole lot back to the store and look hopeless. And pay them to try and figure out what's going on.